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28.03.2013


A good night's rest protects against colds

Men and women who sleep soundly are three to six times less likely to catch cold after being exposed to a cold virus than men and women who sleep badly. Psychologists at Carnegie Mellon University discovered this after performing an experiment that proved how crucial sleep is for the functioning of the immune system.

Sleep & immune system
Once a virus has entered your body your immune system will be better able to fight back if you sleep well. A few days ago we wrote about an experiment that suggests that this is the case. But can good quality sleep also ensure that, if you come into contact with a virus, you don't fall ill? This is the question that Sheldon Cohen wanted to answer so he set up an experiment.

Study
Cohen gave 153 men and women nose drops containing rhinovirus RV-39. Rhinoviruses have perfected the art of entry into the human body via the respiratory airways. There's a picture of one above. Colds are almost always caused by rhinoviruses.

Cohen had questioned his test subjects during the 14 days prior to administering the viruses about the quality of their sleep and their sleep efficiency: the percentage of time spent in bed that the subjects were also actually asleep.

If sleep efficiency is below 85 percent doctors refer to this as having 'sleep problems'. This was the case for just 9 percent of the test subjects.

Both length of sleep and sleep efficiency determined whether a person became ill or not, Cohen discovered. The subjects who slept for 8 hours or longer were 2.9 times less likely to catch cold than the subjects who slept for less than 7 hours. Sleep efficiency had a greater effect, as the figure below shows.

Here the subjects were divided into tertiles according to their sleep efficiency: three equal-sized groups, with relatively low, normal and good sleep efficiency.

Results
The not-so-good sleepers, with a sleep efficiency of less than 92 percent, were 5.5 times more likely to develop a cold than the good sleepers, who had a sleep efficiency of over 98 percent.


A good night's rest protects against colds


Conclusion
The conclusion that the researchers draw is not surprising. "Poorer sleep efficiency and shorter sleep duration in the weeks preceding an exposure to a rhinovirus were associated with lower resistance to illness", they write.

Here you can read more than you could ever possibly want to know about ways and means to improve your sleep.

Source:
Arch Intern Med. 2009 Jan 12;169(1):62-7.

More:
Sleep speeds up post-viral healing 23.03.2013